Device for interferential spectrometry with selective modulation

Abstract

A highly luminous device for interferential spectrometry, comprises a birefringent beam-splitting interferometer combined with an optical system supplying localized fringes. As the beam-splitter element, it has at least one birefringent prism mounted along the optical axis of the device and producing an angular splitting, such as a Wollaston prism, of materials suitable for the construction of such prisms and selected as a function of birefringence and transparent over a wide range of wave lengths. The beam-splitter is placed between a polarizer and an analyzer of variable orientation to obtain flux modulation.

We claim: 
     
       1. A high luminosity device having a light source for interferential spectrometry, which comprises in order from the light source: a polarizer, a birefringent plate, a birefringent beam splitter, an analyzer, an objective lens to bring the beams into interference, a fixed grating located at the focal plane of the objective lens, photoelectric receiver means, and means for causing relative rotation between the polarizer and the analyzer so as to form alternately on the fixed grating a given system of fringes and its complement representing the Fourier transform of the spectral distribution of the source when the polarizer and the analyzer are parallel and perpendicular respectively, said beam splitter comprising two Wollaston prisms mounted along the optical axis, said prisms being made of materials selected as a function of their birefringence and transparent over a wide range of wavelengths. 
     
     
       2. A high luminosity device as defined in claim 1 wherein said Wollaston prisms are identical and are oriented relative to each other such that the axis of the output prism of the first Wollaston prism and the axis of the input prism of the second Wollaston are parallel and the diagonal contact planes of the two Wollaston prisms are parallel. 
     
     
       3. A high luminosity device having a light source for interferential spectrometry, which comprises in order from the light source:a polarizer, a Pockels cell, a birefrigent beam splitter, analyzer, an objective lens to bring the beams into interference, a fixed grating located at the focal plane of the objective lens, and photoelectric receiver means, the Pockels cell being effective to form alternately on the fixed grating a given system of fringes and its complement representing the Fourier transform of the source, said beam splitter comprising two Wollaston prisms mounted along the optical axis of the device and producing angular splitting, said prisms being made of materials selected as a function of their birefringence and transparent over a wide range of wavelengths. 
     
     
       4. A high luminosity device as defined in claim 3 wherein said Wollaston prisms are identical and are oriented relative to each other such that the axis of the output prism of the first Wollaston prism and the axis of the input prism of the second Wollaston are parallel and the diagonal contact planes of the two Wollaston prisms are parallel.